Question 120: Why has Christ commanded us to address God thus: "Our Father"?

Answer: That immediately, in the very beginning of our prayer, he might excite in us a childlike reverence for, and confidence in God, which are the foundation of our prayer: namely, that God is become our Father in Christ, and will much less deny us what we ask of him in true faith, than our parents will refuse us earthly things. (a)

(a) Matt.7:9-11 Or what man is there of you, whom if his son ask bread, will he give him a stone? Or if he ask a fish, will he give him a serpent? If ye then, being evil, know how to give good gifts unto your children, how much more shall your Father which is in heaven give good things to them that ask him?
Luke 11:11-13 If a son shall ask bread of any of you that is a father, will he give him a stone? or if he ask a fish, will he for a fish give him a serpent? Or if he shall ask an egg, will he offer him a scorpion? If ye then, being evil, know how to give good gifts unto your children: how much more shall your heavenly Father give the Holy Spirit to them that ask him?